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PubMed2004

Flexible N,N,N-chelates as supports for iron and cobalt chloride complexes; synthesis, structures, DFT calculations and ethylene oligomerisation studies.

The aryl-substituted N-picolylethylenediamine and diethylenetriamine ligands, (ArNHCH(2)CH(2))[(2-C(5)H(4)N)CH(2)]NH and (ArNHCH(2)CH(2))(2)NH (Ar = 2,6-Me(2)C(6)H(3), 2,4,6-Me(3)C(6)H(2)), have been prepared by employing palladium-catalysed N-C(aryl) coupling reactions of the corresponding primary amines with aryl bromide. Treatment of MCl(2) with (ArNHCH(2)CH(2))[(2-C(5)H(4)N)CH(2)]NH affords [[(ArNHCH(2)CH(2))((2-C(5)H(4)N)CH(2))NH]CoCl(2)](Ar = 2,6-Me(2)C(6)H(3) 1a; 2,4,6-Me(3)C(6)H(2)) 1b and [[(ArNHCH(2)CH(2))((2-C(5)H(4)N)CH(2))NH]FeCl(2)](n)(n= 1, Ar = 2,6-Me(2)C(6)H(3) 2a; n= 2, 2,4,6-Me(3)C(6)H(2) 2b) in high yield. The X-ray structures of 1a and 1b are isostructural and reveal the metal centres to adopt distorted trigonal bipyramidal geometries with the N,N,N-chelates adopting fac-structures. A facial coordination mode of the ligand is also observed in bimetallic 2b, however, in 2a the N,N,N-chelate adopts a mer-configuration with the metal centre adopting a geometry best described as square pyramidal. Solution studies indicate that mer-fac isomerisation is a facile process for these systems at room temperature. Quantum mechanical calculations (DFT) have been performed on 1a and 2a, in which the ligands employed are identical, and show the fac- to be marginally more stable than the mer-configuration for cobalt (1a) while for iron (2a) the converse is evident. Reaction of (ArNHCH(2)CH(2))(2)NH with CoCl(2) gave the five-coordinate complexes [[(ArNHCH(2)CH(2))(2)NH]CoCl(2)](Ar = 2,6-Me(2)C(6)H(3) 3a, 2,4,6-Me(3)C(6)H(2) 3b), in which the ligand adopts a mer-configuration; no reaction occurred with FeCl(2). All complexes 1-3 act as modest ethylene oligomerisation catalysts on activation with excess methylaluminoxane (MAO); the iron systems giving linear alpha-olefins while the cobalt systems give mixtures of linear and branched products.

Journal Article↗
PubMed1999

Bacterial conjugation protein MobA mediates integration of complex DNA structures into plant cells.

Agrobacterium tumefaciens transfers T-DNA to plant cells, where it integrates into the genome, a property that is ensured by bacterial proteins VirD2 and VirE2. Under natural conditions, the protein MobA mobilizes its encoding plasmid, RSF1010, between different bacteria. A detailed analysis of MobA-mediated DNA mobilization by Agrobacterium to plants was performed. We compared the ability of MobA to transfer DNA and integrate it into the plant genome to that of pilot protein VirD2. MobA was found to be about 100-fold less efficient than VirD2 in conducting the DNA from the pTi plasmid to the plant cell nucleus. However, interestingly, DNAs transferred by the two proteins were integrated into the plant cell genome with similar efficiencies. In contrast, most of the integrated DNA copies transferred from a MobA-containing strain were truncated at the 5' end. Isolation and analysis of the most conserved 5' ends revealed patterns which resulted from the illegitimate integration of one transferred DNA within another. These complex integration patterns indicate a specific deficiency in MobA. The data conform to a model according to which efficiency of T-DNA integration is determined by plant enzymes and integrity is determined by bacterial proteins.

Agrobacterium tumefaciens↗
PubMed1991

[Synthesis of partial structure of complex types of N-glycoproteins].

Comparable syntheses of beta-D-GlcpNAc-(1----2)-[beta-D-GlcpNAc-(1----6)]-alpha-D-Manp-(1- ---6)-beta-D-ManpO(CH2)8CO2Me and beta-D-GlcpNAc-(1----2)-alpha-D-Manp-(1----3)-beta-D-ManpO(C H2)8CO2Me with the glycosyl halide and imidate methods were investigated. 3,4,6-Tri-O-acetyl-2-deoxy-(2,2,2-trichloroethoxycarbonylamino)-al pha-D-glucopyranosyl bromide or trichloroacetimidate are suitable glycosyl donors for beta-D-glycoside coupling with secondary hydroxyl groups.

Carbohydrate Sequence↗
PubMed1990

Mucinous cystic neoplasm of the pancreas. Estimation of grade of malignancy with imaging techniques and its surgical implications.

The results of diagnostic imaging procedures, macroscopic and microscopic findings and clinical follow up data of 20 mucinous cystic neoplasms of the pancreas were retrospectively reviewed to determine the grade of malignancy and its surgical implications. The largest mean diameter was 8.9 cm for 10 malignant cases, 5.0 cm for two premalignant cases, and 3.1 cm for eight benign tumours. Ultrasonography or computed tomography or both, corresponded well with macroscopy. The 10 malignant and two premalignant lesions had intracystic mural nodules or extracystic solid components, while the eight benign specimens had neither nodules nor solid portions. Structural complexity seen on ultrasonography or computed tomography, which reflected the irregularity in size and shape of the cysts, internal septa, walls, and solid components, was severe in the 10 malignant and two borderline tumours and mild or moderate in the eight benign lesions. Angiography showed that five of the nine malignant tumours were hypervascular, while the two premalignant and four benign lesions were all avascular. Five of 10 patients with malignant tumours died of local recurrence or remote hematogenous metastases, and one with malignant disease was still alive with liver metastases at the time of writing. We propose that a careful preoperative estimate of the malignant potential of such cysts should be made based on the size of the tumour, the presence of mural nodules and solid areas, and the structural complexity on ultrasonography or computed tomography, as well as the amount of vascularity seen on angiography. Attention should be paid at follow up to the presence of local recurrence and haematogenous metastases in cases of malignant disease.

Adenocarcinoma, Mucinous↗
PubMed2004

Combined transhepatic and transjugular approach for radiofrequency ablation of an accessory pathway in a child with complex congenital heart disease.

We report on a boy with recurrent drug resistant atrioventricular reentrant tachycardia. The patient had complex structural heart disease consisting of right atrial isomerism, systemic venous anomaly (mirror image orientation of the intrathoracic veins, hemiazygos continuation to the left-sided superior vena cava, with separate drainage of the hepatic veins into the left-sided atrium, congenitally corrected transposition (ccTGA), pulmonary atresia (PA), ventricular and atrial septal defects (VSD and ASD). At the age of 22 months RF ablation was performed. Access to the heart was obtained by percutaneous puncture of a hepatic vein, the left internal jugular vein, and femoral artery. Earliest retrograde atrial conduction during tachycardia was localized to the free wall of the left-sided AV groove, and ablation in this area was successful. There were no procedure-related complications. RF ablation of accessory pathway is feasible in young children with complex structural heart disease and abnormal systemic venous return. In such patients access to the heart must be planned with the knowledge of the anatomy and judicious use of the hepatic venous approach, which should be done only by experienced investigators.

Catheter Ablation↗
PubMed1991

Candida albicans mycelial wall structure: supramolecular complexes released by zymolyase, chitinase and beta-mercaptoethanol.

Different techniques released from the wall of Candida albicans mycelial cells high molecular weight mannoprotein materials with different levels of complexity. SDS solubilized among others one protein of 180 kDa which reacted with a monoclonal antibody (MAb) specific of a O-glycosylated protein secreted by regenerating mycelial protoplasts [Elorza et al. (1989) Biochem Biophys Res Commun 162:1118-1125]. Zymolyase, chitinase and beta-mercaptoethanol, released different types of high molecular highly polydisperse mannoprotein materials (greater than 180 kDa) that also reacted with the same MAb. These materials had N-glycosidically linked sugar chains, in addition to the O-glycosidically bonded sugars, as their molecular masses were significantly reduced by Endo H digestion. Besides, the specific materials released by either zymolyase or chitinase seemed to be the same throughout the process of germ tube formation. Transmission electron microscopy of thin sections of cells and walls showed that mannoproteins and chitin are evenly distributed throughout the entire cell wall structure.

Blotting, Western↗
PubMedDate not supplied

[DNA interaction with low molecular ligands of different structure. II. Complexes of DNA with actinomine and its analogs].

DNA-complexes with actinomine and its analogues containing omega-dialkylaminoalkyl groups at 1,9 positions of the phenoxazone moiety were studied by technique of spectrophotometry, viscometry and flow birefringence. In the process of spectrophotometry titration two groups of spectra corresponding to different DNA--ligand ratio in a complex were observed. According to the experimental data the investigated compounds are bounded to DNA by means of intercalation and external binding. There within a region of low degrees of binding the intercalation type of the ligand--DNA interaction prevails. In virtue of the spectrophotometry data the intercalation binding share was calculated. The intrinsic viscosity of a complex increases in the case of ligand intercalation and does not change as it joins to the DNA double-helix from outside. Optical anisotropy of DNA molecule increases linearly irrespective of the way of ligand binding. Data on the flow birefringence permits to conclude that under external binding the angle between the normal to the ligand chromophore plane and the axis of DNA double-helix is about zero. During ligand intercalation the equilibrium rigidity of DNA molecules increases.

Chemical Phenomena↗
PubMed2004

Immunoassay of total prostate-specific antigen using europium(III) nanoparticle labels and streptavidin-biotin technology.

Nanoparticle labels conjugated with biomolecules are used in a variety of different assay applications. We investigated the possibility of using europium(III)-labeled 68-nm nanoparticles coated with monoclonal antibodies or streptavidin (SA) to detect prostate-specific antigen (PSA) in serum. The selection of a suitable antibody pair and interference caused by the combination of nanoparticle label and structurally complex analyte were of special interest. A set of antibodies recognizing different epitope areas of PSA was mapped to find the optimal antibody pair for the immunometric nanoparticle-based assay. Different assay configurations were tested to obtain a good correlation with a conventional method based on biotinylated detection antibodies and europium(III) chelate-labeled streptavidin. Monoclonal capture antibody 5E4 was covalently coated on a microtitration well surface; biotinylated 5H6 monoclonal antibody (Mab) was used for detection, and europium(III)-labeled streptavidin-coated nanoparticles were utilized for signal generation. Total PSA concentrations were determined from a panel of male serum samples to test the developed assay. The correlation of the nanoparticle-based and reference assays was good; y=0.9844x-0.1252, R2=0.98, n=27; and the lowest limit of detection of the assay (LLD=0.83 ng/l) was 35-fold lower than for the reference method. The assay application presented here, where a structurally complex analyte is detected, combines the exceptionally high affinity of streptavidin-biotin technology and the high specific activity of long lifetime fluorescence nanoparticle labels. The general characteristics of this combination should permit the development of various immunoassay applications featuring high sensitivity, rapidity, and low consumption of reagents.

Antibodies, Monoclonal↗
PubMed2005

Spectroscopic and electrochemical studies of ruthenium and osmium complexes of salicylideneimine-2-thiophenol Schiff base.

The reactions between [M(3)(CO)(12)], M = Ru and Os, and salicylideneimine-2-thiophenol Schiff base in THF under reflux gave [Ru(CO)(4)(satpH)] and [Os(CO)(3)(satpH(2))] complexes. Structures of the two complexes were proposed on the basis of spectroscopic studies. Magnetic study of [Ru(CO)(4)(satpH)] suggested that a change in oxidation state of the ruthenium atom from zero to +1 was achieved via oxidative addition of the SH group with a proton displacement to give a low-spin d(7) electronic configuration. UV-Vis spectra of the two complexes in different solvents exhibited visible bands due to metal-to-ligand charge transfer. Electrochemical investigation of the free ligand and complexes showed some cathodic and anodic irreversible peaks due to interconversions through electron transfer.

Electrochemistry↗
PubMed2005

Cortical activation in the processing of passive sentences in L1 and L2: an fMRI study.

The question of whether the bilingual brain processes a first and second language (L1 and L2, respectively) differently is a central issue in many psycholinguistic and neurolinguistic studies. This study used functional magnetic resonance imaging (fMRI) to investigate whether late bilinguals process structurally complex sentences in L1 and L2 in different cortical networks. For this purpose, we directly compared brain activity during the processing of active and passive sentences in both L1 and L2. We asked 36 healthy subjects to judge whether or not a presented sentence was semantically plausible. Both L1 and L2 activated the left hemispheric language-related regions such as the left inferior frontal, superior/middle temporal, and parietal cortices. However, we found different activation patterns between L1 and L2 in the processing of passive sentences. Passive sentences elicited greater activation than their active counterparts in the left pars triangularis, the premotor area, and the superior parietal lobule in Japanese, but not in English. Furthermore, there was a significant interaction between sentence type (active versus passive) and language (Japanese versus English) in the left pars orbitalis. The results of this study indicate that late bilinguals use similar cortical regions to comprehend both L1 and L2. However, when late bilinguals are presented with structurally complex sentences, the involvement of these regions differs between L1 and L2. These results suggest that, in addition to age of L2 acquisition and L2 proficiency, differences in grammatical construction affect cortical representation during the comprehension of L1 and L2.

Adult↗
PubMed2002

The catalytic mechanism of indole-3-glycerol phosphate synthase: crystal structures of complexes of the enzyme from Sulfolobus solfataricus with substrate analogue, substrate, and product.

Indoleglycerol phosphate synthase catalyzes the ring closure of an N-alkylated anthranilate to a 3-alkyl indole derivative, a reaction requiring Lewis acid catalysis in vitro. Here, we investigated the enzymatic reaction mechanism through X-ray crystallography of complexes of the hyperthermostable enzyme from Sulfolobus solfataricus with the substrate 1-(o-carboxyphenylamino) 1-deoxyribulose 5-phosphate, a substrate analogue and the product indole-3-glycerol phosphate. The substrate and the substrate analogue are bound to the active site in a similar, extended conformation between the previously identified phosphate binding site and a hydrophobic pocket for the anthranilate moiety. This binding mode is unproductive, because the carbon atoms that are to be joined are too far apart. The indole ring of the bound product resides in a second hydrophobic pocket adjacent to that of the anthranilate moiety of the substrate. Although the hydrophobic moiety of the substrate moves during catalysis from one hydrophobic pocket to the other, the triosephosphate moiety remains rigidly bound to the same set of hydrogen-bonding residues. Simultaneously, the catalytically important residues Lys53, Lys110 and Glu159 maintain favourable distances to the atoms of the ligand undergoing covalent changes. On the basis of these data, the structures of two putative catalytic intermediates were modelled into the active site. This new structural information and the modelling studies provide further insight into the mechanism of enzyme-catalyzed indole synthesis. The charged epsilon-amino group of Lys110 is the general acid, and the carboxylate group of Glu159 is the general base. Lys53 guides the substrate undergoing conformational transitions during catalysis, by forming a salt-bridge to the carboxylate group of its anthranilate moiety.

Binding Sites↗
PubMed2002

Segmental linkage disequilibrium within the dopamine transporter gene.

The dopamine transporter gene (DAT) has been implicated in a variety of disorders, including bipolar disorder, attention-deficit hyperactivity disorder, cocaine-induced paranoia, Tourette's syndrome, and Parkinson's disease. As no clear functional polymorphism has been identified to date, studies rely on linkage disequilibrium (LD) to assess the possible genetic contribution of DAT to the various disorders. A better understanding of the complex structure of LD across the gene is thus critical for an accurate interpretation of the results of such studies, and may facilitate the mapping of the actual functional variants. In the process of characterizing the extent of variation within the DAT gene, we have identified a number of single nucleotide polymorphisms (SNPs) suitable for LD studies, 14 of which have been analyzed, along with a 3' repeat polymorphism, in a sample of 120 parent-proband triads. Calculations of pairwise LD between the SNPs in the parental haplotypes revealed a high degree of LD (P < 0.00001) in the 5' (distal promoter through intron 6) and 3' (exon 9 through exon 15) regions of DAT. This segmental LD pattern is maintained over approximately 27 kb and 20 kb in these two regions, respectively, with very little significant LD between them, possibly due to the presence of a recombination hotspot located near the middle of the gene. These analyses of the DAT gene thus reveal a complex structure resulting from both recombination and mutation, knowledge of which may be invaluable to the design of future studies.

Dopamine Plasma Membrane Transport Proteins↗
PubMed2004

Constraints on evolution and postcopulatory sexual selection: trade-offs among ejaculate characteristics.

Ejaculates function as an integrated unit to ensure male fertility and paternity, can have a complex structure, and can experience multiple episodes of selection. Current studies on the evolution of ejaculates typically focus on phenotypic variation in sperm number, size, or related traits such as testes size as adaptations to postcopulatory male-male competition. However, the evolution of the integrated nature of ejaculate structure and function depends on genetic variation in and covariation between the component parts. Here we report a quantitative genetic study of the components of the ejaculate of the cockroach Nauphoeta cinerea, including those we know to experience postcopulatory sexual selection, in the context of functional integration of ejaculate characters. We use the patterns of genetic variation and covariation to infer how the integration of the functions of the ejaculate constrain and shape its evolution. Ejaculate components were highly variable, showed significant additive genetic variance, and moderate to high evolvability. The level of genetic variation in these characters, despite strong directional or truncating selection, may reflect the integration of multiple episodes of selection that occur in N. cinerea. There were few significant phenotypic correlations, but all the genetic correlations among ejaculate characters were significantly different from zero. The patterns of genetic variation and covariation suggest that there are important trade-offs among individual traits of the ejaculate and that evolution of ejaculate characteristics will not proceed unconstrained. Fully describing the genetic relationships among traits that perform as an integrated unit helps us understand how functional relationships constrain or facilitate the evolution of the complex structure that is the ejaculate.

Analysis of Variance↗
PubMed2003

Three-dimensional visualization of insect morphology using confocal laser scanning microscopy.

Cuticular structures of insects are often microscopic and intricately complex; among the most complex structures are male genitalia. Genitalic structures are essential in taxonomic and phylogenetic studies of insects. Using well-described species from two disparate dipteran genera, we demonstrate the utility of confocal laser scanning microscopy for studying the morphological characters of fly genitalia by taking advantage of the autofluorescent properties of cuticle material. Reconstructions of confocal data sets obtained from genitalic structures embedded in two commonly used entomological mounting media (euparal and glycerin jelly) are presented. Aberration artefacts often observed in confocal data obtained from thick specimens were analysed and strategies for their minimization are discussed. Our results indicate that confocal laser scanning microscopy and 3D reconstruction are excellent techniques for visualizing small, complex, autofluorescent structures in flies. These techniques could have a profound impact on the quality of information provided by 3D representations of insect structures over more traditional methods of visualization.

Animals↗
PubMed1995

Modal and temporal analysis of head mathematical models.

The basic hypotheses used during these investigations were based on the vibration analysis of the head, which demonstrated that the head is not a solid nondeformable body, but a complex structure including deformable elements. Laboratoire des Systemes Biomecanique (LSBM) has recently proposed three mathematical models: a lumped model, a finite element model of the head in its sagittal plane, and a three-dimensional finite element model. These models were validated by their modal behavior and enabled the lesion mechanisms to be distinguished as a function of the spectral characteristics of the shock. The objective of this study is to complete these modal results by temporal analysis of the models by calculating the evolution of the intracranian mechanical parameters under shock conditions. To describe the head's dynamic behavior in the temporal domain, constant energy shocks of variable duration were simulated to evaluate their influence on different quantities as the intracerebral stresses in terms of compression, tensile, and shearing stresses, the relative brain-skull displacement, and the skull deformation. The importance of modal behavior of the head is illustrated by analyzing its temporal response to variable duration impacts, thus exciting very different frequencies. For a triangular shock, the critical duration times are between 10 and 15 x 10(-3) s, which correspond to impacts that excite the first resonance frequency of the head. Taking modal behavior into consideration in developing the finite element model leads to a harmonization of the calculated intracerebral stresses, even for short duration shocks. So, when the head is considered as a complex structure made up of several deformable elements, risk limitation is conditioned by an impact energy reduction for frequencies close to the natural frequencies of the structure. In the time field, the objective will be to avoid a number of impact shapes and durations. Therefore, the aim will not be to dampen the impact at any cost, but to damper it in an "intelligent" manner. In the future, this will allow the reduction of an injury mechanism-related risk, without increasing the risk of an injury generated by another mechanism.

Biomechanical Phenomena↗
PubMed2001

Foam cell formation containing lipid droplets enriched with free cholesterol by hyperlipidemic serum.

A monoclonal antibody, ASH1a/256C (256C), which binds to atherosclerotic lesions in Watanabe heritable hyperlipidemic rabbit (WHHL) aorta in vivo, recognizes complex structures of phosphatidylcholine mixed with neutral lipids. In the present study, a cell culture system is described in which foam cells express 256C-positive lipid droplets. J774.1 macrophages were incubated in the presence of a small volume of WHHL serum for 24 h to produce foam cells, which were then incubated without the WHHL serum for 3 days. Oil red O-positive lipid droplets appeared on day 1, and were present in the cells during the whole incubation period. The lipid droplets in the cells were positively immunostained with antibody 256C on day 4, although they were negative on day 1. Expression of the antigenic lipid droplets was also induced by the addition of acetylated LDL or sera from patients with hyperlipidemia. When foam cells were induced by the addition of WHHL serum, cellular content of cholesteryl ester was greatly increased but then decreased to near basal levels by day 4. Concomitantly, cellular free cholesterol increased during the culture period, indicating that the cholesteryl ester changes to free cholesterol by day 4. The lipid droplets in the foam cells on day 4 were positively stained with filipin, a fluorescent probe for free cholesterol, as well as with 256C antibody, indicating that free cholesterol is enriched in antigenic lipid droplets. These observations suggest that hydrolysis and rearrangement of cellular cholesterol take place in foam cells to form complex structures of phosphatidylcholine and free cholesterol in lipid droplets.

Animals↗
PubMed2000

Structure and proteoglycan composition of specialized regions of the elastic tendon of the chicken wing.

The elastic tendon of the avian wing has been described by others as a unique structure with elastic properties due to the predominance of elastic fibers in the midsubstance. Further analyses of the tendon have shown it to possess five anatomically distinct regions. Besides the major elastic region, a distally located fibrocartilage and three tendinous regions are present. The tendinous regions connect: (1) the muscle to the elastic region, (2) the elastic region to the fibrocartilage and (3) the latter to the insertion site. The elastic region possesses thick and abundant elastic fibers and very thin, interconnecting collagen fibers. The collagen fibers in the sesamoid fibrocartilage are thick and interwoven, defining spaces occupied by fibrochondrocytes embedded in a non-fibrillar and highly metachromatic matrix. Biochemical analyses have shown that the fibrocartilage has about tenfold the amount of glycosaminoglycans (GAGs) found in the other regions. The main GAG in this region was chondroitin sulfate (CS) (plus keratan sulfate as detected immunocytochemically), while the other regions showed variable amounts of CS, dermatan sulfate (DS) and heparan sulfate. Further analyses have shown that a large CS-bearing proteoglycan is found in the fibrocartilage. The elastic region possesses two main proteoglycans, a large CS-bearing proteoglycan (which reacted with an antibody against keratan sulfate after chondroitinase ABC treatment) and a predominant DS-bearing proteoglycan, which showed immunoreactivity when assayed with an anti-biglycan antibody. The results demonstrate that the elastic tendon is a complex structure with complex regional structural and compositional adaptations, suited to different biomechanical roles.

Animals↗
PubMedDate not supplied

A scanning and transmission electron microscopy study of the parabronchial unit in quail (Coturnix coturnix) and town pigeons (Columba livia).

A combined scanning electron (SEM) and transmission electron microscopy (TEM) investigation was undertaken to gain insight into the complex structural pattern of the atrial compartment and the gas exchange tissue of parabronchial units in quail and town pigeons. The aim was also to depict the changes taking place in the parabronchial unit in the late prehatching and early posthatching periods in quail. The standard SEM and TEM investigation was carried out in 13 mature quail and 8 town pigeons. The developmental study involved embryonic quail (Days 15, 16, 17), newly hatched quail, quail 24 h after hatching, and quail aged 2, 10, 19, and 25 days (3 individuals per group). The luminal relief of the parabronchus is formed by anastomosing interatrial septa delineating the atrial pits, which are thinner and shallower in pigeons. The atrial bottom opens in mature individuals into 3-6 infundibula. The extracellular material represented by trilaminar substance, which does not appear until hatching, veils the surface relief of the parabronchial epithelium, which is consequently hardly accessible to three-dimensional visualization. Only in town pigeons with fewer discontinuous layers of extracellular material was it possible to visualize the surface of the atrial epithelium, that is, of the granular and squamous atrial cells. The SEM analysis has convincingly shown the intricate spatial organization of atria, infundibula, and air and blood capillaries of the gas exchange tissue. The retinacula, that is, parallelly arranged processes of squamous respiratory cells bridging the air-capillary lumina, were evidenced by SEM and TEM. The complex structure of the avian parabronchus has been successfully demonstrated in the present SEM and TEM study.

Animal Structures↗